The Effects Are IN The Guitar? It’s So Simple…

We’ve all had that problem. Up on stage, rocking out Jimi Hendrix-style on guitar with your band, but frustrated at having to mess around with foot pedals to control all of the effects. [Richard] solved this problem in a unique way: he put a preamp and a microcontroller in a guitar that can create some very interesting effects.

For the musically challenged, electric guitars often have several sets of electromagnetic pickups that detect vibrations in the strings at different points along the strings. Selecting different pickup combinations with a built-in switch changes the sound that the guitar makes. [Richard] wired the pickups in his Fender Stratocaster to the microcontroller and programmed it to switch the pickups according to various patterns. The effect is somewhat like a chorus pedal at times and it sounds very unique.

The volume and tone knobs on the guitar are used to select the programmed patterns to switch various pickups at varying speeds. This has the added bonus of keeping the stock look of the guitar in tact, unlike some other guitars we’ve seen before. The Anubis preamp, as it is called, is a very well polished project and the code and wiring schematic are available on the project site along with some audio samples.

21 thoughts on “The Effects Are IN The Guitar? It’s So Simple…

  1. At best a mild chorus. Using a micro would lead to “zipper pots” Instead of VCA’s. Looks like a big dis-assembly to change the throw away battery.
    My sustaining steel has everything on board. From lithium power thru an onboard Digitech RP70 20w amp and speaker.

  2. The audio quality can be vastly improved by buffering the pickups with opamps or even transistor followers. (Guitar pickups are high impedance sources…) Also, it’s possible to design it such that the entire circuit can be powered from a bias (e.g. 12V with a few hundred ohms of series resistance) applied on the audio output.

    1. Thanks for the suggestions, Mike. For some reason I thought at first it would be nice to try to electrically mimic passive circuits. That’s why I have the pickups going straight to a 1 meg ohm digital pot. When I revise it I think I’ll buffer the pickups with opamps. In place of the digipots I’ll use a VCA (maybe an SSM2164) and have inverted and non-inverted signals from each pickup going to separate VCA’s instead of using the analog switches. I’ll low pass filter the PWM outputs of the Atmega to control the VCA’s.

      For the external power, do you just put 12 V on the tip of the phone plug and assume the amp or effect on the other end has isolation caps?

  3. Hm, this is a nice hack, but at some point we need to ask: does it make sense?

    What we got here is basically a chorus + flanger effect. Something you sure could have packed into a footpedal or any other box as well. Effectively, the guy has turned a versatile musical instrument (a Strat-style electric guitar) into a one-trick pony that can only do this kind of effect.

    So while I’m all for new ways in guitar electrics, this is a cul de sac. I’ll pass on that one.

  4. Three classmates and I did this as our freshman engineering project almost 15 years ago. We put chorus, distortion, tremolo, bass, and a tuner in the guitar and made the whole thing wireless. Pretty sure kids have been doing this sort of thing for a while now.

  5. Some of you are missing the point here, this is a very cool idea which can only be implemented easily on board the guitar as it uses the actual variation of the sounds produced by multiple pickups – this would not work with a Les Paul Jr. for instance as this guitar has only one pickup. I would like to see an analog implementation using opto isolaters and LFO’s, in fact maybe I will build one for one of my strat’s and include a stereo circuit as well. Good work!

    1. Thanks, Miles. I’m certainly not suggesting that my pickup mixer should be used alone instead of effects pedals. The point is that when you select 1 pickup combination, you’re stuck with that combination of nodes and antinodes due to the position along the string. You can use filters to get rid of harmonic content, but you can’t fill in the notches (except for with distortion from overdrive, but that’s different). My recording is dry just to demonstrate what the pickup mixer sounds like alone. The current design demonstrates the concept, but has serious problems.

      I like your idea of using vactrols/optoisolators and using oscillators for control. That will overcome the zipper noise that I’m getting. Let me know if you try it out. My next attempt will involve VCA’s. A completely different method would be to have an output jack for each pickup and then modulate them all on a laptop with Pure Data, Max/MSP, a SynthEdit VST, or something similar.

      1. Richard, Cheap 3 pickup output cable (if you are using only the standard strat out of phase middle pickup for phase option) would be VGA cables which have three shielded coax for the three pickups, just got a couple of brand new in the plastic ones at local thrift store for a buck each and you can get pc mount mating connectors online for around 50 cents each in 10 packs, shipping included. as a bonus you get a bunch of lines you can use for power, logic, etc. just DON’T plugin to your laptop VGA port!

  6. I rather like my Peavey AT-200 guitar. They actually use a hex pickup for their integrated effects board to apply effects on a per-string basis. This also makes for an interesting user interface where you have to pluck certain string / fret combos to enable specific effects.

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